The requirements for Vitis vinifera grapes are long, warm to hot, dry summers and mild winters. The optimum amount of rainfall is 22 inches annually. Irrigation is also desirable and often essential from spring continuing until harvest. One reason California produces such great grapes is the state generally has dry weather in late spring and summer. Too much rain at this time can cause grey rot and other diseases. A rainy summer can also push back harvest. Rainfall right before harvest causes the vines to eagerly suck up the water throwing the sugar/acidity balance off.
In regions like Bordeaux, “inclement harvest season weather” makes the harvesting of Cabernet Sauvignon a little earlier than ideal and thus requires blending of other grapes to “fill in the gaps.” As global warming has increased the number of warm vintage years, the need for blending is based more on ideology and tradition. Cabernet Sauvignon is very rarely planted any further north than Bordeaux due to its late ripening requiring a warm climate to reach optimum ripeness. If the climate is too cool there is a potential for more herbaceous and green bell pepper flavors from less than ideally ripening grapes.
Further north in Burgundy, pinot noir thrives due to it being an early ripener and the climate is ideal where warm weather ends quickly.
The main wine producing climate lies below the 50th parallel. Above this line, the climate is too cold. Germany, the most northerly wine region in the world, situates their vineyards around rivers which moderate the temperatures. The vineyards face south or south-west to angle towards the sun where the slate soil in the steep valleys absorb the sun’s heat and retain it overnight. White grape varieties such as Riesling, Mueller-Thurgau and Gewurztraminer do best here.
In the Piedmont region of Italy, the warmer south-facing slopes are mainly used to grow Nebbiolo or Barbera grapes; the cooler sites are planted with Dolcetta or Moscato.
In Tuscany, the area has a warm Mediterranean climate where the Sangiovese grape performs best where it can receive direct sunlight with the many hillside vineyards.
There is a danger that climate change could crush the wine industry in California. A 2 degree rise in temperature could make Napa Valley Chardonnay a thing of the past. A couple more degrees and Napa would no longer be prime territory for wine of any kind. Warmer winters would hinder bud development. Napa Valley region is blessed with a 64 degree average temperature that falls in the middle of the comfort zones of many varietals including Merlot, Syrah and Cabernet Sauvignon. But……Napa barely hits the range for Chardonnay grapes which thrive in the 57 to 63 degree temperatures. Even 1 degree could push Napa into questionable territory for Chardonnay.
Mankind manages to overcome/adjust to changes when necessary. I’m sure if the need comes to change what we are familiar with, to that which will work more efficiently……so be it. We shall overcome!
(Part 1 of this post was published on April 24)
Marie Griffin, West/Northwest Florida Wine Supervisor